//validate dutch telephone number
function validTel(string) 
{
	var Chars = "0123456789- ";
	//check chars
	var deLengte = string.length;
	for(var i=0; i<string.length; i++) {
		if(Chars.indexOf(string.charAt(i))==-1)
		return false;
	}
	//length
	if(deLengte<10)
	{
		return(false);
	}
	return true;
}

//trim value
function trim(value) {
	value = value.replace(/^\s+/,'');
	value = value.replace(/\s+$/,'');
	return value;
}

function checkform()
{
	//fields to be checked
	var my_fields= new Array()
	my_fields["naam"]="Naam";
	my_fields["telefoon"]="Telefoon";

	for(var field in my_fields) {
		//set value
		var value=trim(document.getElementById(field).value);

		//check value
		if(value=="") {
			document.getElementById(field).style.border='1px solid #FF0000';
			document.getElementById(field).focus();
			alert("Het veld '"+my_fields[field]+"' is verplicht");
			return false;
		}else{
			document.getElementById(field).style.border='';
		}

		if(field=="telefoon") {
			if(!validTel(value)) {
				document.getElementById(field).style.border='1px solid #FF0000';
				alert("U dient het veld '"+my_fields[field]+"' geldig in te vullen");
				return false;
			}else{
				document.getElementById(field).style.border='';
			}
		}
	}
	return true;
}